Water Cycle

• Where water comes from

  • Volcanoes
  • The ocean
  • Geysers
  • Asteroids
  • Natural springs
  • People
  • Plants
  • Burning
• The global hydrological cycle operates as a closed system driven by solar energy and gravitational potential energy
• In a closed system, there is a fixed amount of water in the Earth-atmosphere system estimated at 1385 million km3
• A closed system does not have any external inputs or outputs, so the total volume of water is constant and finite
• Water can exist in different states within the closed system (liquid, vapour, and solid)
• The Hydrological Cycle has key components: Stores, Fluxes, Processes
• In the last Ice Age, more water was held within the cryosphere in a solid form as snow and ice, leading to lower sea levels
• Recent climate warming is causing major losses of ice in Greenland and Antarctica, resulting in significant rises in sea level
• Humans have built water storage reservoirs to increase the security of their water supplies
• The oceans contain an estimated 96.5 to 97% of the world's total water
• Residence times impact turnover within the water cycle system
• Some ancient groundwater, like that found deep below the Sahara Desert, is termed fossil water and is not renewable for human use
• Major ice sheets store water as ice for very long periods
• Groundwater, if deep-seated, can spend over 10,000 years beneath the Earth's surface
• Ice core dating has suggested that the residence time of some water in Antarctic ice is over 800,000 years
• The drainage basin is an open system where things can be taken away and put into it
• Long term water residence times

  • Ocean- 3,600 years
  • Ice caps- 15,000 years
  • Rocks- lithosphere
• Short term water residence times

  • Atmosphere- 10 days
  • Soil moisture- 2-50 weeks
• Transfer methods

  • Rivers
  • Fluxes
  • Evaporation
  • Transpiration
• Major physical systems where water is stored

  • Hydrosphere- all of Earth's water, including surface water, groundwater, snow and ice, and water in the atmosphere
  • Lithosphere- the hard, rigid outer part of the Earth
• Transfer

  • Rivers
  • Fluxes
  • Evaporation
  • Transpiration
• Major physical systems storing water

  • Hydrosphere
  • Lithosphere
  • Cryosphere
  • Atmosphere
  • Biosphere
• Orographic rainfall occurs when air is forced to cool when it rises over relief such as hills or mountains
• Convectional rainfall happens when the Sun heats up the ground, warming the air until it cools down and rains again
• Morphology


  (not provided)
• Impacts of climate

  • Refill
  • Rain
  • Floods
  • Flush
• Impacts of soil

  • Less soil = more runoff
  • Saturated
• Sea ice grows and shrinks seasonally as the oceans around the poles freeze. It does not affect sea levels and is closely linked to climate
• Ice shelves are glaciers or ice caps extending over the ocean. They can break up into ice caps, contributing to sea level rise
• Glaciers and ice sheets are found on land, with the largest being the Greenland ice sheet and Antarctic Ice sheets. They are formed by the build-up and compression of snow
• Snowfall falls and melts seasonally, providing an input into river systems
• Permafrost is ground frozen for more than two consecutive summers, with extensive areas in Northern Canada and Siberia
• Water is lost through pores and transferred to the atmosphere via transpiration. Rates can depend on the seasons, time, and the vegetation itself
• Evapotranspiration (EVT) is when water returns to the atmosphere through evaporation and transpiration combined, with losses being purely evaporative
• Potential evapotranspiration (PEVT) is the maximum rate at which transpiration could occur
• Carbon dioxide diffuses into the ocean carbon cycle via the air-sea surface exchange molecules of CO2 entering the ocean by diffusing into the sea surface waters and dissolving, a physicochemical process
• The amount of CO2 that diffuses and dissolves in the sea surface water depends on variables such as wind, sea surface mixing, concentrations of CO2, and the temperature of the water
• Once dissolved in surface seawater, CO2 can enter the ocean through three mechanisms: the ocean biological pump, the oceanic carbonate pump, and the physical carbon pump/Thermohaline Circulation
• The ocean biological pump is driven by organisms in the ocean, transforming carbon compounds into new forms, moving carbon throughout the ocean, and down to the sea floor sediments
• Marine snow is a shower of organic material falling from upper waters to the deep ocean, including biological debris and other inorganic matter